Laser direct structuring of solar cells

LIMO Lissotschenko Mikrooptik GmbH has advanced the "Gaussian-to-TopHat converter" with integrated scan technique to a closed module with a complete "optical core", especially suitable for the patterning of six-inch solar wafers.
 
"Our goal has been an all-in-one solution for producers of solar cells," explains Dr. Oliver Homburg, Director for Advanced Optical Solutions at LIMO. The g2T scanning system combines the advantages of two different optical concepts: It converts Gaussian beams into homogeneous "TopHat" profiles that provide high precision trenches with smooth edges rather than the typical saw-tooth pattern. Moreover, integrated galvo mirrors and a specially modified F-Theta lens allow fast and accurate scanning. The system was especially designed for laser direct structuring of materials with single-mode lasers (532 nm). On account of the 160 by 160 mm² large scan field it is primarily suitable for solar technology.
 
First successes of the Fraunhofer Institute for Solar Energy Systems (ISE) at Freiburg in applying this technology boosted LIMO to further development. The new system received a complete "optical core," delivered pre-assembled and -adjusted by the Dortmund-based company. The customer may integrate the module with an optional control unit in their system on demand. The system is outstanding due to its operating with distinctly increased process stability. Photovoltaic manufacturers notably place value on this characteristic and on potential inline-capable upgrade (integration into existing processes).
 
With a spot size of 75 times 75 µm², the scanning speed increased to now about 20 m/s. "Solar cells can now be processed even more precise, faster and therefore more cost-effective than before”, says Dr. Homburg. “The system is particularly suited to local structuring of the material. On that account, crucial characteristics are scanning speed, homogeneity of the written lines and the flexibility to freely program and quickly change the cell design.” LIMO showcased the g2T scanning system in May at LASER World of PHOTONICS in Munich.

Contact: Dr. Oliver Homburg, LIMO
o.homburg@limo.de